// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#include "settings.h"
#include "test.h"
#include "imgui/imgui.h"

enum
{
  e_maxBodies = 256
};

// This test demonstrates how to use the world ray-cast feature.
// NOTE: we are intentionally filtering one of the polygons, therefore
// the ray will always miss one type of polygon.

// This callback finds the closest hit. Polygon 0 is filtered.
class RayCastClosestCallback : public b2RayCastCallback
{
public:
  RayCastClosestCallback()
  {
    m_hit = false;
  }

  float ReportFixture(b2Fixture* fixture, const b2Vec2& point, const b2Vec2& normal, float fraction) override
  {
    uintptr_t index = fixture->GetUserData().pointer;
    if (index == 1)
    {
      // By returning -1, we instruct the calling code to ignore this fixture and
      // continue the ray-cast to the next fixture.
      return -1.0f;
    }

    m_hit = true;
    m_point = point;
    m_normal = normal;

    // By returning the current fraction, we instruct the calling code to clip the ray and
    // continue the ray-cast to the next fixture. WARNING: do not assume that fixtures
    // are reported in order. However, by clipping, we can always get the closest fixture.
    return fraction;
  }
  
  bool m_hit;
  b2Vec2 m_point;
  b2Vec2 m_normal;
};

// This callback finds any hit. Polygon 0 is filtered. For this type of query we are usually
// just checking for obstruction, so the actual fixture and hit point are irrelevant. 
class RayCastAnyCallback : public b2RayCastCallback
{
public:
  RayCastAnyCallback()
  {
    m_hit = false;
  }

  float ReportFixture(b2Fixture* fixture, const b2Vec2& point, const b2Vec2& normal, float) override
  {
    uintptr_t index = fixture->GetUserData().pointer;
    if (index == 1)
    {
      // By returning -1, we instruct the calling code to ignore this fixture and
      // continue the ray-cast to the next fixture.
      return -1.0f;
    }

    m_hit = true;
    m_point = point;
    m_normal = normal;

    // At this point we have a hit, so we know the ray is obstructed.
    // By returning 0, we instruct the calling code to terminate the ray-cast.
    return 0.0f;
  }

  bool m_hit;
  b2Vec2 m_point;
  b2Vec2 m_normal;
};

// This ray cast collects multiple hits along the ray. Polygon 0 is filtered.
// The fixtures are not necessary reported in order, so we might not capture
// the closest fixture.
class RayCastMultipleCallback : public b2RayCastCallback
{
public:
  enum
  {
    e_maxCount = 3
  };

  RayCastMultipleCallback()
  {
    m_count = 0;
  }

  float ReportFixture(b2Fixture* fixture, const b2Vec2& point, const b2Vec2& normal, float) override
  {
    uintptr_t index = fixture->GetUserData().pointer;
    if (index == 1)
    {
      // By returning -1, we instruct the calling code to ignore this fixture and
      // continue the ray-cast to the next fixture.
      return -1.0f;
    }

    b2Assert(m_count < e_maxCount);

    m_points[m_count] = point;
    m_normals[m_count] = normal;
    ++m_count;

    if (m_count == e_maxCount)
    {
      // At this point the buffer is full.
      // By returning 0, we instruct the calling code to terminate the ray-cast.
      return 0.0f;
    }

    // By returning 1, we instruct the caller to continue without clipping the ray.
    return 1.0f;
  }

  b2Vec2 m_points[e_maxCount];
  b2Vec2 m_normals[e_maxCount];
  int32 m_count;
};


class RayCast : public Test
{
public:

  enum Mode
  {
    e_any = 0,
    e_closest = 1,
    e_multiple = 2
  };

  RayCast()
  {
    // Ground body
    {
      b2BodyDef bd;
      b2Body* ground = m_world->CreateBody(&bd);

      b2EdgeShape shape;
      shape.SetTwoSided(b2Vec2(-40.0f, 0.0f), b2Vec2(40.0f, 0.0f));
      ground->CreateFixture(&shape, 0.0f);
    }

    {
      b2Vec2 vertices[3];
      vertices[0].Set(-0.5f, 0.0f);
      vertices[1].Set(0.5f, 0.0f);
      vertices[2].Set(0.0f, 1.5f);
      m_polygons[0].Set(vertices, 3);
    }

    {
      b2Vec2 vertices[3];
      vertices[0].Set(-0.1f, 0.0f);
      vertices[1].Set(0.1f, 0.0f);
      vertices[2].Set(0.0f, 1.5f);
      m_polygons[1].Set(vertices, 3);
    }

    {
      float w = 1.0f;
      float b = w / (2.0f + b2Sqrt(2.0f));
      float s = b2Sqrt(2.0f) * b;

      b2Vec2 vertices[8];
      vertices[0].Set(0.5f * s, 0.0f);
      vertices[1].Set(0.5f * w, b);
      vertices[2].Set(0.5f * w, b + s);
      vertices[3].Set(0.5f * s, w);
      vertices[4].Set(-0.5f * s, w);
      vertices[5].Set(-0.5f * w, b + s);
      vertices[6].Set(-0.5f * w, b);
      vertices[7].Set(-0.5f * s, 0.0f);

      m_polygons[2].Set(vertices, 8);
    }

    {
      m_polygons[3].SetAsBox(0.5f, 0.5f);
    }

    {
      m_circle.m_radius = 0.5f;
    }

    {
      m_edge.SetTwoSided(b2Vec2(-1.0f, 0.0f), b2Vec2(1.0f, 0.0f));
    }

    m_bodyIndex = 0;
    memset(m_bodies, 0, sizeof(m_bodies));

    m_degrees = 0.0f;

    m_mode = e_closest;
  }

  void Create(int32 index)
  {
    if (m_bodies[m_bodyIndex] != NULL)
    {
      m_world->DestroyBody(m_bodies[m_bodyIndex]);
      m_bodies[m_bodyIndex] = NULL;
    }

    b2BodyDef bd;

    float x = RandomFloat(-10.0f, 10.0f);
    float y = RandomFloat(0.0f, 20.0f);
    bd.position.Set(x, y);
    bd.angle = RandomFloat(-b2_pi, b2_pi);

    if (index == 4)
    {
      bd.angularDamping = 0.02f;
    }

    m_bodies[m_bodyIndex] = m_world->CreateBody(&bd);

    if (index < 4)
    {
      b2FixtureDef fd;
      fd.shape = m_polygons + index;
      fd.friction = 0.3f;
      fd.userData.pointer = index + 1;
      m_bodies[m_bodyIndex]->CreateFixture(&fd);
    }
    else if (index < 5)
    {
      b2FixtureDef fd;
      fd.shape = &m_circle;
      fd.friction = 0.3f;
      fd.userData.pointer = index + 1;
      m_bodies[m_bodyIndex]->CreateFixture(&fd);
    }
    else
    {
      b2FixtureDef fd;
      fd.shape = &m_edge;
      fd.friction = 0.3f;
      fd.userData.pointer = index + 1;

      m_bodies[m_bodyIndex]->CreateFixture(&fd);
    }

    m_bodyIndex = (m_bodyIndex + 1) % e_maxBodies;
  }

  void DestroyBody()
  {
    for (int32 i = 0; i < e_maxBodies; ++i)
    {
      if (m_bodies[i] != NULL)
      {
        m_world->DestroyBody(m_bodies[i]);
        m_bodies[i] = NULL;
        return;
      }
    }
  }

  void UpdateUI() override
  {
    ImGui::SetNextWindowPos(ImVec2(10.0f, 100.0f));
    ImGui::SetNextWindowSize(ImVec2(210.0f, 285.0f));
    ImGui::Begin("Ray-cast Controls", nullptr, ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoResize);

    if (ImGui::Button("Shape 1"))
    {
      Create(0);
    }

    if (ImGui::Button("Shape 2"))
    {
      Create(1);
    }

    if (ImGui::Button("Shape 3"))
    {
      Create(2);
    }

    if (ImGui::Button("Shape 4"))
    {
      Create(3);
    }

    if (ImGui::Button("Shape 5"))
    {
      Create(4);
    }

    if (ImGui::Button("Shape 6"))
    {
      Create(5);
    }

    if (ImGui::Button("Destroy Shape"))
    {
      DestroyBody();
    }

    ImGui::RadioButton("Any", &m_mode, e_any);
    ImGui::RadioButton("Closest", &m_mode, e_closest);
    ImGui::RadioButton("Multiple", &m_mode, e_multiple);

    ImGui::SliderFloat("Angle", &m_degrees, 0.0f, 360.0f, "%.0f");

    ImGui::End();
  }

  void Step(Settings& settings) override
  {
    Test::Step(settings);

    g_debugDraw.DrawString(5, m_textLine, "Shape 1 is intentionally ignored by the ray");
    m_textLine += m_textIncrement;
    switch (m_mode)
    {
    case e_closest:
      g_debugDraw.DrawString(5, m_textLine, "Ray-cast mode: closest - find closest fixture along the ray");
      break;
    
    case e_any:
      g_debugDraw.DrawString(5, m_textLine, "Ray-cast mode: any - check for obstruction");
      break;

    case e_multiple:
      g_debugDraw.DrawString(5, m_textLine, "Ray-cast mode: multiple - gather multiple fixtures");
      break;
    }

    m_textLine += m_textIncrement;

    float angle = b2_pi * m_degrees / 180.0f;
    float L = 11.0f;
    b2Vec2 point1(0.0f, 10.0f);
    b2Vec2 d(L * cosf(angle), L * sinf(angle));
    b2Vec2 point2 = point1 + d;

    if (m_mode == e_closest)
    {
      RayCastClosestCallback callback;
      m_world->RayCast(&callback, point1, point2);

      if (callback.m_hit)
      {
        g_debugDraw.DrawPoint(callback.m_point, 5.0f, b2Color(0.4f, 0.9f, 0.4f));
        g_debugDraw.DrawSegment(point1, callback.m_point, b2Color(0.8f, 0.8f, 0.8f));
        b2Vec2 head = callback.m_point + 0.5f * callback.m_normal;
        g_debugDraw.DrawSegment(callback.m_point, head, b2Color(0.9f, 0.9f, 0.4f));
      }
      else
      {
        g_debugDraw.DrawSegment(point1, point2, b2Color(0.8f, 0.8f, 0.8f));
      }
    }
    else if (m_mode == e_any)
    {
      RayCastAnyCallback callback;
      m_world->RayCast(&callback, point1, point2);

      if (callback.m_hit)
      {
        g_debugDraw.DrawPoint(callback.m_point, 5.0f, b2Color(0.4f, 0.9f, 0.4f));
        g_debugDraw.DrawSegment(point1, callback.m_point, b2Color(0.8f, 0.8f, 0.8f));
        b2Vec2 head = callback.m_point + 0.5f * callback.m_normal;
        g_debugDraw.DrawSegment(callback.m_point, head, b2Color(0.9f, 0.9f, 0.4f));
      }
      else
      {
        g_debugDraw.DrawSegment(point1, point2, b2Color(0.8f, 0.8f, 0.8f));
      }
    }
    else if (m_mode == e_multiple)
    {
      RayCastMultipleCallback callback;
      m_world->RayCast(&callback, point1, point2);
      g_debugDraw.DrawSegment(point1, point2, b2Color(0.8f, 0.8f, 0.8f));

      for (int32 i = 0; i < callback.m_count; ++i)
      {
        b2Vec2 p = callback.m_points[i];
        b2Vec2 n = callback.m_normals[i];
        g_debugDraw.DrawPoint(p, 5.0f, b2Color(0.4f, 0.9f, 0.4f));
        g_debugDraw.DrawSegment(point1, p, b2Color(0.8f, 0.8f, 0.8f));
        b2Vec2 head = p + 0.5f * n;
        g_debugDraw.DrawSegment(p, head, b2Color(0.9f, 0.9f, 0.4f));
      }
    }

#if 0
    // This case was failing.
    {
      b2Vec2 vertices[4];
      //vertices[0].Set(-22.875f, -3.0f);
      //vertices[1].Set(22.875f, -3.0f);
      //vertices[2].Set(22.875f, 3.0f);
      //vertices[3].Set(-22.875f, 3.0f);

      b2PolygonShape shape;
      //shape.Set(vertices, 4);
      shape.SetAsBox(22.875f, 3.0f);

      b2RayCastInput input;
      input.p1.Set(10.2725f,1.71372f);
      input.p2.Set(10.2353f,2.21807f);
      //input.maxFraction = 0.567623f;
      input.maxFraction = 0.56762173f;

      b2Transform xf;
      xf.SetIdentity();
      xf.position.Set(23.0f, 5.0f);

      b2RayCastOutput output;
      bool hit;
      hit = shape.RayCast(&output, input, xf);
      hit = false;

      b2Color color(1.0f, 1.0f, 1.0f);
      b2Vec2 vs[4];
      for (int32 i = 0; i < 4; ++i)
      {
        vs[i] = b2Mul(xf, shape.m_vertices[i]);
      }

      g_debugDraw.DrawPolygon(vs, 4, color);
      g_debugDraw.DrawSegment(input.p1, input.p2, color);
    }
#endif
  }

  static Test* Create()
  {
    return new RayCast;
  }

  int32 m_bodyIndex;
  b2Body* m_bodies[e_maxBodies];
  b2PolygonShape m_polygons[4];
  b2CircleShape m_circle;
  b2EdgeShape m_edge;
  float m_degrees;
  int32 m_mode;
};

static int testIndex = RegisterTest("Collision", "Ray Cast", RayCast::Create);
